A. Field
The present invention relates to a method and an apparatus for testing value documents, in particular bank notes, in order to determine value document properties.
B. Related Art
Value documents within the terms of the present invention in particular are bank notes, but also other documents and deeds requiring protection such as for example checks, share certificates, ID cards, passports, admission tickets, public transport tickets and the like.
Characteristic properties of these value documents are checked for determining their authenticity. For this purpose most different sensors adapted to the particular properties to be checked are used. With the help of optical sensors, for example, the absorption, transmission and/or luminescence properties of value documents can be tested.
Due to the daily use some types of value documents may show signs of wear. This in particular is the case with bank notes, which in the course of time crumple and the surfaces of which soil. Both signs of wear lead to an asymmetric reflection behavior. In order to being able to reliably test such value documents with the help of optical sensors, the value document area to be tested is illuminated simultaneously from various directions. In this way the optical sensors are insensitive to the above-mentioned asymmetric effects.
But value documents are not only tested as to their authenticity, they are also checked as to their fitness for circulation. Therefore, additional sensors are used in order to check exactly those properties that mainly have asymmetric effects in their reflection behavior, which because of the special illumination are not detectable with the help of the above-mentioned optical sensors, i.e. in particular, for example, crumples and soiling.
The problem of the present invention is to propose a simplified method and a simplified apparatus for testing value documents, in order to capture value document properties independently of asymmetric effects of the value document as well as the asymmetric effects of the value document.
This problem is solved by a method and an apparatus having the features of the independent patent claims. In claims dependent thereon advantageous developments and embodiments of the invention are specified.